In 1977 there was introduced the quantum-well (QW) laser, a laser that in the active region employs one or more thin quantum well layers (Lz less than about 400 Å) sandwiched in a thicker wavequide region that is further enclosed by still higher gap p-type and n-type confining layers (see E. A. Rezek, N. Holonyak, Jr., B. A. Vojak, G. E. Stillman, J. A. Rossi, D. L. Keune, and J. D. Fairing, “LPE In1-xGaxP1-zAsz (x˜0.12, z˜0.26) DH Laser With Multiple Thin-Layer (<500 Å) Active Region,” Appl. Phys. Lett., vol 31, pp 288–290, Aug. 15, 1977; E. A. Rezek, H. Shichijo, B. A. Vojak, and N. Holonyak, Jr., “Confined-Carrier Luminescence of a Thin In1-xGaxP1-zAsz Well (x˜0.13, z˜0.29; ˜400 Å) in an InP p-n Junction,” Appl. Phys. Lett., vol. 31 pp. 534–536, Oct. 15, 1977). For about ten years, numerous groups have been trying to convert the quantum well laser, which is practical and widely manufactured, into a so-called quantum-dot laser. The goal has been to build an ultimate laser. In theory, the thin quantum well layer (or layers) of a QW laser is “cut-up” into (ideally) a uniform dense sheet of identical little quantum boxes (i.e., quantum dots). With such a structure, instead of the electrons and holes being injected (via current, light, etc.) and collected in an easily grown thin (Lz less than about 400 Å) uniform QW sheet (thus with one dimensional thickness confinement and quantization; a 2-D structure), the electrons and holes are collected and recombine in the little quantum dots (i.e., quantum boxes; hence, three-dimensional confinement and quantization; a 0-D structure). The little boxes, or dots, are like “fat” little molecules and (ideally) all alike and densely and uniformly arranged. [Reference can be made, for example, to U.S. Pat. No. 6,369,403, and to J. H. Ryou, R. Dupuis, G. Walter, D. Kellog, N. Holonyak, Jr., D. Mathes, R. Hull, C. Reddy, and V. Narayanamurti, Appl. Phys. Lett. 78, 4091 (2001).] Actually, the quantum dots are stochastic and probabilistic, small but random. They are random in geometry, in size, and in arrangement - - - and not dense enough, i.e., are not in sufficient proximity to be quantum coupled (by tunneling). Electron-hole (e-h) pairs are stuck in each box (assuming they are collected at all) and don't transport to neighboring boxes. The e-h pairs don't move around and re-arrange in the plane of the dots as readily as they do in a thin QW sheet (Lz less than about 400 Å; Lx, Ly extended in the plane; hence a 2-D structure). In short, there is little or no conduction along the sheet (or sheets) of quantum dots.
It is among the objects of the present invention to provide devices, and methods of making same, which are responsive to the foregoing limitations of the prior art, and to also provide devices which exhibit improved operation as light emitters and as other applications.